1. Field of the Invention
The present invention relates generally to the field of peristaltic pumps. More particularly, the present invention relates to a tube loading assembly comprising a tube pressing member riding on one arm of a two-arm torsion spring.
2. Description of the Related Art
A peristaltic pump moves and meters liquid through tubing of a dispensing circuit free of ambient contaminants. The dispensing circuit is releasably mounted to the pump and the tubing of the dispensing circuit is loaded in the pump. The rotating pump drives liquids through the tubing of the dispensing circuit. In a hospital or lab setting, the liquid transferred are body fluids, intravenous solutions, extracorporeal bloods, reagent solutions, nutrient culture media, etc.
A peristaltic pump assembly usually includes a base, a motor, a rotor assembly with circulating tube occluding rollers, and a tube pressing member with a tube track or raceway. In such arrangement, the space between rollers on the rotor and the pressing member is less than the diameter of the tubing and the tubing must be squeezed in. How one loads the tubing decides further variations of the assembly.
Early peristaltic pumps rely on hand-feeding for tube loading. Its benefit in structural simplicity is compromised because both hands are needed at the same time. Retractable mechanisms to move either the sliding rollers or the pressing member away from one another during tube loading are less cumbersome but add parts and cost, e.g., in both U.S. Pat. No. 4,256,442 to Lamadrid & Cullis and U.S. Pat. No. 4,599,055 to Dykstra, a movable pressing member is pivotally mounted on the base and allows single-handed tube loading. Further improvements allow automatic loading of the tubing loop to pump through progressively tightened space between rollers on a rotor and the housing of the modified pressing member (e.g. U.S. Pat. No. 4,861,242 to Finsterwald), or through a rotor with tube guiding grooves and notch to lower the tubing into the raceway (as in U.S. Pat. No. 5,387,088 to Knapp et al.), or through a further simplified self-loading version (as in U.S. Pat. No. 7,018,182 to O'Mahony & Behan). These improvements also aid loading of a disposable tube section into the pump between a pressing raceway and a rotor before use. Also available is a disposable tube cassette and the likes for use in a peristaltic pump as in U.S. Pat. No. D264,134 to Xanthopoulos. Methods for its quick loading and unloading are also desirable.
To accommodate a collapsible and resilient tube of different materials, sizes and degrees of compressibility, the tube pressing member and the opposing sliding rollers must be urged toward and occlude the tube section for fluid transfer. This tube compression force must not be so tight as to damage the tube or so loose as to lose pressure for flow. To prolong tube flex life, U.S. Pat. No. 4,559,040 to Horres & Moers has a removable pumping chamber portion so the tubing may be stored in the pump head without being pinched by the eccentric rotor. The device in U.S. Pat Pub 2006/0083644 (Zumbrum & Coates III) uses location of flanged ends of tubing section to absorb part of the tubing tension thereby extending its flex life. Further improvements employ means for dynamic compression force which gradually closes in or increases upon fluid entry and gradually opens up or decreases before exit. They are represented in U.S. Pat. No. 5,110,270 to Morrick using spring-loaded sliding rollers and in U.S. Pat. No. 5,230,614 to Zanger et al., in which a specific arcuate surface on one pressing pump head to move a fluid through the tube in one direction without creating undue fluid back pressure in an opposite direction. Reduced fluid pulsation or back mixing is a feature important for steady and precision dosing by a peristaltic pump.
Besides tube loading, tube caring and dynamic compression mechanisms tend to be mechanically complex, they are also difficult to make and use. Accordingly, the main objective of the present invention is a peristaltic pump that is simple to make, easy to load, unload and store, especially with a disposable tube section, not prone to finger pinching and does not aggravate the tubing flex or the inherent fluid pressure pulsation issue.